Articles, devices, systems, and methods for solar energy storage and/or utilization

ABSTRACT

The present invention generally relates to articles, devices, systems, and methods relating to the storage of solar energy and/or solar energy utilization. In some embodiments, the articles, devices, and systems may be used to carry out photocatalytic reactions, for example, the photocatalytic production of oxygen and/or hydrogen gases from water.

RELATED APPLICATIONS

The present application claims priority to U.S. provisional application, U.S. Ser. No. 61/583,244, filed Jan. 5, 2012, entitled “ARTICLES, DEVICES, SYSTEMS, AND METHODS FOR SOLAR ENERGY STORAGE AND/OR UTILIZATION,” by Bulovic et al., herein incorporated by reference.

FIELD OF THE INVENTION

The present invention generally relates to articles, devices, systems, and methods relating to the storage of solar energy and/or solar energy utilization. In some embodiments, the articles, devices, and systems may be used to carry out photocatalytic reactions, for example, the photocatalytic production of oxygen and/or hydrogen gases from water.

BACKGROUND OF THE INVENTION

The ability to store solar energy remains a significant obstacle to widespread solar energy utilization. The sun transmits energy to the earth in the form of visual light and thermal radiation. In an effort to conserve natural resources and optimize energy usage, it is desirable to harness this solar energy for various practical applications. Solar energy can be converted via various technologies into other forms of applicable energy, including electrical and hydrothermal. Unfortunately, existing systems and methods fail to efficiently utilizes both the visual and/or thermal properties of solar energy.

Therefore, there is a need for improved systems and methods.

SUMMARY OF THE INVENTION

In some embodiments, an article for carrying out an photochemical oxidation and/or reduction reaction at the surface of water is provided, the article comprising a first anode; a first cathode; and a first photoactive material, wherein at least a portion of the first photoactive material is in electrical communication with the first anode and the first cathode, wherein the article has a density less than or equal to the density of water such that at least a portion of the article, when placed in water, is above the surface of the water. In some embodiments, the article further comprises a second anode; a second cathode, wherein the second cathode is not in physical contact with the second anode; and a second photoactive material, wherein at least a portion of the second photoactive material is in contact with the second anode and the second cathode, wherein the second anode is in contact with the first cathode and the second cathode is not in contact with the first anode, or alternatively, wherein the second cathode is in contact with the first anode and the second anode is not in contact with the first cathode.

In some embodiments, a device is provided comprising a first anode and a first cathode, wherein the first cathode is not in physical contact with the first anode; a first photoactive material section, wherein at least a portion of the first photoactive material section is in contact with the first anode and the first cathode; a second anode and a second cathode, wherein the second cathode is not in physical contact with the second anode; and a second photoactive material section, wherein at least a portion of the second photoactive material section is in contact with the second anode and the second cathode, wherein the second anode is in contact with the first cathode and the second cathode is not in contact with the first anode, or alternatively, wherein the second cathode is in contact with the first anode and the second anode is not in contact with the first cathode.

In some embodiments, a method of forming oxygen and hydrogen gases from water is provided, comprising providing a device, comprising a first anode and a first cathode, wherein the first cathode is not in physical contact with the first anode; a first photoactive material section, wherein at least a portion of the first photoactive material section is in contact with the first anode and the first cathode; a second anode and a second cathode, wherein the second cathode is not in physical contact with the second anode; and a second photoactive material section, wherein at least a portion of the second photoactive material section is in contact with the second anode and the second cathode, wherein the second anode is in contact with the first cathode and the second cathode is not in contact with the first anode, or alternatively, wherein the second cathode is in contact with the first anode and the second anode is not in contact with the first cathode, and wherein the device does not comprise an external power source; and exposing the device to electromagnetic radiation thereby forming oxygen gas at the at least one anode and hydrogen gas at the at least one cathode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1J and 2A-2B depict non-limiting examples of articles of the present invention, according to some embodiments.

FIGS. 3A-3F depict non-limiting examples of devices of the present invention, according to some embodiments.

FIG. 4 depicts a non-limiting example of the steps for forming an article or device of the present invention, according to some embodiments.

FIG. 5 depicts a non-limiting example of a gas collection system, according to some embodiments.

Other aspects, embodiments, and features of the invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings. The accompanying figures are schematic and are not intended to be drawn to scale. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention. All patent applications and patents incorporated herein by reference are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control.

DETAILED DESCRIPTION

The present invention generally relates to articles, devices, systems, and methods relating to the storage of solar energy and/or solar energy utilization. In some cases, the present invention relates to self-contained, integrated articles, devices, and/or systems that are capable of converting solar energy into storable fuels, for example, hydrogen fuels. In some cases, the articles, devices, system, and methods utilize of at least one photoactive material. In some cases the articles, devices, systems, and methods allow for efficient light harvesting and higher photon-to-fuel conversion as compared to known articles, devices, systems, and methods.

According to some aspects of the present invention, the articles, devices, and/or systems are provided for a variety of applications. In some embodiments, the articles, devices, and/or systems may be used for photocatalytic reactions. Photocatalysis (e.g., involving an oxidation and/or reduction reaction) may occur upon exposure of the articles, devices, and/or systems to electromagnetic radiation, without the need for an external voltage source. For example, in some cases, the articles, devices, and/or systems allow for the conversion of water to hydrogen gas and/or oxygen gas without use of an external power and/or energy source. Thus, energy can be stored, via a reactive pathway involving articles, devices, and/or systems of the invention, in the form of oxygen gas and/or hydrogen gas. It should be noted that while the photocatalytic production of hydrogen and/or oxygen gases from water is discussed in many embodiments described herein, this is by no means limiting, and other photocatalytic reactions may be carried out using the articles, devices, and systems of the present invention.

Generally, the articles, devices, and systems described herein comprise at least one anode, at least one cathode, and at least one photoactive material region. Upon exposure to electromagnetic radiation, charge separation may occur in the photoactive material region, wherein electron and electron holes are formed. The electrons may be transported to the cathode and the electron holes may be transported to the anode, wherein the holes/electrons can react with a water molecule (or other reactant), resulting in the formation of oxygen gas and/or hydrogen gases (or other products).

In some embodiments, the present invention provides an article, wherein the article comprises a first anode, a first cathode, and a first photoactive material section. The article may optionally comprise a core material. Generally, the first cathode is not in physical contact with the first anode and at least a portion of the first photoactive material section is an electrical communication with the first anode and the first cathode. In some cases, the first anode, first cathode, and first photoactive material section, and optionally the core material, are integrally connected. The first anode, first cathode, and first photoactive material section may be oriented (e.g., about a core material) such that upon exposure to electromagnetic radiation, the article is capable of converting a fuel, such as water, into an oxidized and a reduced product, such as oxygen gas and hydrogen gas. The products formed may be isolated and used for further reaction, for example, to combine and reform energy and the original fuel.

FIG. 1 depicts non-limiting examples of articles comprising a first anode, a first cathode, a first photoactive material section. As described herein, an article may be formed and/or provided in a variety of suitable shapes, sizes, and arrangements, and accordingly, an articles is not limited to the shapes, sizes, and arrangements depicted in FIG. 1. FIG. 1A depicts article 1 comprising first anode 2, first cathode 4, first photoactive material section 6, and core material 8. In FIG. 1A, the article is spherical, but those of ordinary skill in the art will recognize other suitable shapes. In this figure, first anode 2 and first cathode 4 are in direct electrical communication with first photoactive material section 6. Each of first anode 2, first cathode 4, and first photoactive material section 6 are integrally connected with core material 8. FIG. 1B shows another suitable arrangement, wherein first anode 2 and first cathode 4 are in direct electrical communication with first photoactive material section 6.

As noted herein, in some cases, the anode and/or cathode may be in indirect electrical communication with the photoactive material. That is, a conductive material may be interposed between the anode and/or cathode and the photoactive material. For example, as depicted in FIG. 1C, first conductive material 10 is located between first cathode 4 and first photoactive material section 6, and in FIG. 1D, second conductive material 12 is located between first anode 2 and first photoactive material section 6 and first conductive material 10 is located between first cathode 4 and first photoactive material section 6. In should be understood, that the arrangement depicted in FIG. 1D may alternatively be described as the anode comprising two materials/sections (e.g., materials/sections 2 and materials/sections 12) and the cathode comprising two materials/sections (e.g., materials/sections 4 and materials/sections 10). Each anode and/or cathode described herein may comprise one material/section, or alternatively, more than one material/section (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, or more, materials/sections).

It should be understood, that for the articles and devices described and depicted herein, the anode(s) and cathode(s) may be swapped. For example, FIG. 1E shows a similar structure as shown in FIG. 1B, except anode 2 and cathode 4 have switched locations.

“Electrical communication,” as used herein, is given its ordinary meaning as would be understood by those of ordinary skill in the art whereby electrons can flow between components in a facile enough manner for the components to operate as described herein. In some cases, the components may be in “direct electrical communication” with each other. “Direct electrical communication,” as used herein, is given its ordinary meaning as defined above with respect to electrical communication, but in this instance, the two components are in direct contact with one another (e.g., as opposed to through a secondary material, through use of circuitry, etc.). In other embodiments, two components may be in “indirect electrical communication” with each other. That is, a material and/or circuitry may be interposed between the two components. Generally, the interposed material is conductive or substantially conductive thus allowing for ease of transport of electrons between the two components.

In some embodiments, components of the articles, devices, and systems as described herein may be integrally connected. The term “integrally connected,” when referring to two or more components, objects, or materials, means components, objects, and/or materials that do not become separated from each other during the course of normal use, e.g., separation requires at least the use of tools, and/or by causing damage to at least one of the components, objects, and/or materials for example, by breaking, peeling, dissolving, etc.

In some embodiments, an anode and/or cathode may be associated with anodic catalytic material and/or cathodic catalytic material, respectively. For example, as shown in FIG. 1F, first anode 2 is associated with first anodic catalytic material 14 and first cathode 4 is associated with first cathodic catalytic material 16. Catalytic materials are described in more detail herein.

In some cases, at least a portion of the article is encapsulated with an encapsulant material. In some cases, the encapsulant material may protect one or more of the materials associated with the article which may be sensitive to the environmental conditions about the article and/or prevent the article from shorting. For example, in some cases, the photoactive material may be sensitive to environmental conditions such as water and/or oxygen, and thus, the photoactive material (e.g., which is not otherwise encapsulated by another component of the article) may be encapsulated with an encapsulant material. For example, as shown in FIG. 1G, first photoactive material section 6 is encapsulated with first encapsulant material 18. In some cases, the encapsulant material may be formed such that at least a portion of at least one anode and at least a portion of one cathode is not encapsulated with the encapsulant materials such that the portion of the anode and the portion of the cathode may be exposed to a reactant (e.g., such that an oxidation and/or reduction action may be carried out using the article). Furthermore, following formation of the encapsulant material, the portion of the anode and/or cathode which is not encapsulated may be extended beyond the encapsulant material following formation of the encapsulant material to provide sufficient surface area of the anode/cathode to carry out the oxidation/reduction reactions.

FIG. 1H shows a non-limiting example of an article comprising first anode 2, first cathode 4, first photoactive material section 6, core material 8, first anodic catalytic material 14, first cathodic catalytic material 16, and encapsulant material 18.

As will be understood by those of ordinary skill in the art, if the articles depicted in FIG. 1 are to be exposed to electromagnetic radiation via the direction indicated by arrow 11, the components situated above photoactive material 6 (e.g., cathode 4 in FIG. 1B, anode 2 in FIG. 1E, encapsulant material 18 in FIGS. 1G and 1H, cathode 4 and encapsulant material 18 in FIGS. 1I and 1J) should be transparent and/or substantially transparent to allow for transmission of the electromagnetic radiation to the photoactive material. If the device will be inverted and/or exposed to electromagnetic radiation via the direction indicated by arrow 13, the components situated below photoactive material 6 (e.g., core 8 in FIGS. 1A-1J, anode 2 in FIGS. 1B and 1H, cathode 4 in FIG. 1E, etc.) should be transparent and/or substantially transparent to allow for transmission of the electromagnetic radiation to the photoactive material. Those or ordinary skill in the art will be able to apply these teaching to other arrangements of an article.

In some embodiments, an article (e.g., as described above in any one of FIG. 1A-1J, or as contemplated by this disclosure) (or device, as described herein) has a density less than or equal to the density of water. This may allow at least a portion of the article, when the article is placed in water, to be above the surface of the water. The ability for the article to float at or above the surface of the water may be advantageous as it may allow the article to be exposed to electromagnetic radiation directly as opposed to the electromagnetic radiation having to pass through water before reaching the article (e.g., in the case of articles which are submerged). In some cases the first anode and the first cathode are situated about an article such that at least a portion of the first anode and the first cathode are in contact with the photoactive material, as well as are in contact with the water. Therefore, upon exposure to electromagnetic radiation, the photoactive material may produce electrons and electron holes, which can be transferred to the portions of the first anode and the first cathode in contact with water, respectively, wherein oxygen and/or hydrogen gases may be formed. In some embodiments, an article (or device, as described herein) may have a density less than or equal to 0.99 g/mL, less than or equal to 0.98 g/mL, less than or equal to 0.97 g/mL, less than or equal to 0.95 g/mL, less than or equal to 0.9 g/mL, less than or equal to 0.85 g/mL, less than or equal to 0.80 g/mL, less than or equal to 0.7 g/mL, less than or equal to 0.6 g/mL, less than or equal to 0.5 g/mL, less than or equal to 0.4 g/mL, less than or equal to 0.3 g/L, less than or equal to 0.2 g/mL, or less than or equal to 0.1 g/mL. In some embodiments, an article (or device, as described herein) may have a density between about 0.90 g/mL and less than 1 g/mL, between about 0.95 g/mL and less than 1 g/mL, between about 0.97 g/mL and less than 1 g/mL, between about 0.98 g/mL and less than 1 g/mL, or between about 0.99 g/mL and less than 1 g/mL.

For example, as shown in FIG. 1I, an article is provided comprising first anode 2, first cathode 4, first photoactive material 6, core material 8, first anodic catalytic material 14, and encapsulant material 18, the density of the article is selected such that first portion 24 of the article is situated below water line 22 and second portion 26 of the article is situated above water line 22. In some cases, the density of the article and the orientation of the first photoactive material about the article are selected such that the photoactive material is substantially above the water line, and a portion of at least one anode and at least one cathode are below the water line and exposed to the water. For example, as shown in FIG. 1I, first photoactive material section 6 is above water line 22 and encapsulated by encapsulant material 18 such that first photoactive material section 6 is not directed exposed to the surrounding environmental conditions including the water, and portion 27 of anode 2 associated with first anodic catalytic material 14 is exposed to the water and portion 27 of the cathode 4 is exposed to the water.

In some cases, an article further comprises a stabilizing fin that aids in orienting the article in a suitable direction in the water. For example, as shown in FIG. 1I, stabilizing fin 20 helps to keep the article in an upright direction in the water. A similar example is depicted in FIG. 1J. In FIGS. 1I and 1J, upon exposure to electromagnetic radiation, water may be split to form oxygen gas at anode 2 (e.g., via anodic catalytic material 14) and/or hydrogen gas may be formed at cathode 4.

In some embodiments, an article may take an inverted configuration as compared to the articles described in FIG. 1. For example, as shown in FIG. 2A, an article is shown comprising first anode 2, first cathode 4, first photoactive material section 6, and optionally first anodic catalytic material 14 and first cathodic catalytic material 16. In this figure, the core material comprises first component 28 and the second component 30. Generally, component 28 is transparent or substantially transparent to allow for exposure of first photoactive material section 6 to electromagnetic radiation. Yet another example of an inverted article is shown in FIG. 2B, wherein core material comprises first component 28, second component 30 and third component 32. Each of the components of the core material may comprise the same composition or may comprise different compositions. For example, the compositions of the core material portions may be selected so as to provide the article with a selected density such that a portion of the article (e.g., 26) is above the water line 22 and a portion of the article (e.g., 24) is below the water line. The articles in FIGS. 2A and 2B each also comprise stabilizing fin 20. In these figures, upon exposure to electromagnetic radiation, water may be split to form oxygen gas at anode 2 (e.g., via anodic catalytic material 14) and/or hydrogen gas may be formed at cathode 4 (e.g., via cathodic catalytic material 16).

It should be understood, that in all of the articles shown in FIG. 1 or FIG. 2, each of the sections drawn as the first anode 2 or the first cathode 4 may optionally comprise more than one material. For example, as noted above, a photoactive material may be in indirect electrical communication with the anode and/or the cathode, and accordingly, a portion of the anode 2 drawn in each of the figures may comprise a conductive material such that anode 2 is in indirect electrical communication with first photoactive material section 6 and/or such that cathode 4 is in indirect electrical communication with first photoactive material section 6.

Those of ordinary skill in the art will be able to select suitable materials, orientations, configurations, sizes, and shapes of the articles shown in FIGS. 1 and 2 based on ordinary knowledge in the art and teachings of the specification.

It should also be understood, that each article as described herein may optionally comprise more than one anode, more than one cathode, more than one area of photoactive material section, and/or more than one catalytic material (e.g., anodic and/or cathodic catalytic materials). For example, in one embodiment, an article may comprise a core material, a first anode, a second anode, a first cathode, a second cathode, a first photoactive material section, and a second photoactive material section, wherein each of the components can be arranged about the core material in a suitable arrangement. In some embodiments, the multiple anodes, cathodes, and/or photoactive material sections may be arranged about the core material as described in detail herein relating to the devices. As a non-limiting example, the first cathode is not in physical contact with the first anode, at least a portion of the first photoactive material section is in electrical communication with the first anode and the first cathode, the second cathode is not in physical contact with the second anode, at least a portion of the second photoactive material section is in contact with the second anode and the second cathode, and the second anode is in contact with the first cathode and the second cathode is not in contact with the first anode, or alternatively, the second cathode is in contact with the first anode and the second anode is not in contact with the first cathode. The first photoactive material section and the second photoactive material section may be the same or different.

In some embodiments, devices are provided. The devices may be employed in similar means as described above with relation to the articles. A device generally comprises a plurality of anodes, cathodes, and photoactive material sections. Each of the anodes may comprise the same or different material. Each of the cathodes may comprise the same or different material. Each of the photoactive material sections may comprise the same or different photoactive composition. In some embodiments, each of the anodes comprise the same or substantially similar material, each of the cathodes comprise the same or substantially similar material, and each of the photoactive material sections comprise the same or substantially similar material.

The components of the device (anodes, cathodes, photoactive material sections) may be arranged about the device such that the anodes and cathodes are in series. Without wishing to be bound by theory, the devices described herein may be designed and arranged such that the total voltage of the device, when exposed to electromagnetic radiation, is sufficient to carry out an oxidation reaction at at least one anode and/or a reduction reaction at at least one cathode. For example, in a particular embodiment, upon exposure to electromagnetic radiation, the voltage of the device may be at least 1.23 V, or greater than 1.23 volts, such that the device is capable of promoting the conversion of water to oxygen and/or hydrogen gases.

In some embodiments, a device comprises a first anode, a first cathode, a second anode, a second cathode, a first photoactive material section, and a second photoactive material section. The first photoactive material section and the second photoactive material section may be the same or different. In this embodiment, the first cathode is not in physical contact with the first anode, at least a portion of the first photoactive material section is in contact with the first anode and the first cathode, the second cathode is not in physical contact with the second anode, the second photoactive material section is in contact with the second anode and the second cathode, and the second anode is in contact with the first cathode and the second cathode is not in contact with the first anode, or alternatively, the second cathode is in contact with the first anode and the second anode is not in contact with the first cathode. That is, each set of anode/cathode/photoactive material section (e.g., first anode/cathode/photoactive material section, second anode/cathode/photoactive material section, etc.) is arranged such that each set of anode/cathode/photoactive material can operate individually as a cell, but the arrangement between the different sets of anode/cathode/photoactive material sections (e.g., between the first anode/cathode/photoactive material section and the second anode/cathode/photoactive material section) is such that the first set and the second set are in series (e.g., wherein the first anode is in contact with the second cathode, or the first cathode is in contact with the second anode).

A non-limiting example of a device is depicted in FIGS. 3A and 3B, wherein first anode 50, first cathode 54, first photoactive material section 52, second anode 56, second cathode 60, and second photoactive material section 58 are formed on core material 62 (e.g., comprising a non-conductive material). In FIG. 3A, first cathode 54 and second anode 56 are in direct contact (e.g., are in direct electrical communication), and in FIG. 3B, first cathode 54 and second anode 56 are in indirect electrical communication (e.g., via material 64). An oxidation reaction may be carried out at first anode 50 and a reduction reaction may be carried out at second cathode 60.

A device (and/or article) may comprise any selected total number of anodes, cathodes, and photoactive material section. Generally, a device comprises the same or substantially similar numbers of anodes and cathodes. In some cases, the device may comprise the same number of photoactive material sections as compared to anodes and/or cathodes. Alternatively, the device may comprise a fewer numbers of photoactive material section as compared to anodes and/or cathodes. That is, each set of anode/cathode may optionally share the same photoactive material as another anode/cathode set.

In some cases, a device comprises at least two anodes and/or cathodes, at least two anodes and/or cathodes, at least three anodes and/or cathodes, at least four anodes and/or cathodes, at least five anodes and/or cathodes, at least eight anodes and/or cathodes, at least ten anodes and/or cathodes, at least twelve anodes and/or cathodes, at least fifteen anodes and/or cathodes, at least twenty anodes and/or cathodes, at least thirty anodes and/or cathodes, at least forty anodes and/or cathodes, at least fifty anodes and/or cathodes, at least seventy-five anodes and/or cathodes, at least one hundred anodes and/or cathodes, or more. In some cases, a device comprises two anodes and/or cathodes, three anodes and/or cathodes, four anodes and/or cathodes, five anodes and/or cathodes, six anodes and/or cathodes, seven anodes and/or cathodes, eight anodes and/or cathodes, nine anodes and/or cathodes, ten anodes and/or cathodes, twelve anodes and/or cathodes, fifteen anodes and/or cathodes, twenty anodes and/or cathodes, or more

Another non-limiting example of a device is shown in FIG. 3C, wherein the left portion of the figure shows the design of a plurality of anodes (e.g., twelve anodes 70 formed on core material 72), the center portion of the figure shows the design of a plurality of cathodes (e.g., twelve cathodes 74), and the right portion of the figure shows the overall device comprising twelve anodes 70 formed on core material 72, three photoactive material sections 76 formed on core material 72 following formation of twelve anodes 70, and twelve cathodes 74 formed following formation of photoactive material sections 76. FIG. 3D shows a cross-section area of the device in FIG. 3C.

The device may be of any suitable size and shape, for example, as described herein. In addition, a device (e.g., as described above in FIG. 3) may or might not a density less than or equal to the density of water, and may optionally comprise a stabilizing fin, at least one catalytic material, an encapsulant material, and/or other components.

In some cases, at least a portion of the device may be encapsulating in an encapsulant material. The encapsulant material may provide protection for the at least one anode, the at least one cathode, and/or the at least one photoactive material from environmental factors for example, as described above with respect to articles. This may be of particular importance in embodiments where the device is to be exposed to water.

In some embodiments, the device may further comprise at least one catalytic material (e.g., an anodic catalytic material, a cathodic catalytic material). An anodic catalytic material may be formed on at least a portion of at least one anode (e.g., the first anode). A cathodic catalytic material may be formed on at least a portion of at least one cathode (e.g., the cathode furthest away from the first anode in series).

Another non-limiting of a cross-section of a device of the present invention comprising an encapsulant material is shown in FIG. 3E. The device in this figure is similar to the device depicted and described in FIGS. 3C and 3D. In this figure, however, the photoactive material and the majority of the anodes and cathodes shown in FIGS. 3C and 3D have been encapsulated by encapsulant material 84. In addition, first anode has been extended such that first anode 80 extends beyond encapsulant material 84 and the cathode furthest in series from the first anode (e.g., cathode 82) has been extended beyond encapsulant material 84. First anode 80 and cathode 82 may be extended using the same or different materials as originally formed on core material 72. The oxidation reaction may occur at first anode 80 and the reduction reaction may occur at cathode 82, upon exposure of the device to electromagnetic radiation.

As will be understood by those of ordinary skill in the art, if the device depicted in FIG. 3E is to be exposed to electromagnetic radiation via the direction indicated by arrow 81, the components situated above photoactive material 76 (e.g., cathodes 74 and 82, encapsulant material 84, anode 80) should be transparent and/or substantially transparent to allow for transmission of the electromagnetic radiation to the photoactive material. If the device will be inverted and/or exposed to electromagnetic radiation via the direction indicated by arrow 83, the components situated below photoactive material 76 (e.g., core 72, anodes 80 and 70) should be transparent and/or substantially transparent to allow for transmission of the electromagnetic radiation to the photoactive material. Those or ordinary skill in the art will be able to apply these teaching to other arrangements of a device.

FIG. 3F shows another variation of a device, similar to that depicted in FIG. 3E, but further comprising anodic catalytic material 86 associated with anode 80 and cathodic catalytic material 88 associated with cathode 82.

Those of ordinary skill in the art will be able to select suitable materials, orientations, configurations, sizes, and shapes of the articles shown in FIGS. 1 and 2 and the articles shown in FIG. 3 based on ordinary knowledge in the art and teachings of the specification.

The anodes, cathodes, and/or photoactive material sections of the device and/or article can be arranged in any suitable manner. For example, the components may be arranged in a linear fashion, in a grid fashion, a circular fashion (e.g., spiral), etc. The components may be arranged vertically (e.g., on the surface of a core material) and/or horizontally (e.g., stacking of components).

In some embodiments, a system is provided comprising a plurality of articles and/or a plurality of devices as described herein. For example, the system may comprise a solution (e.g., water), wherein a plurality of the articles and/or the plurality of devices are provided to the water. In some cases, a system comprises a plurality of articles and/or devices, where each of the articles and/or devices has a density less than or equal to the density of water such that at least a portion of each article, when placed in water, is above the surface of the water. For example, the system may comprise a plurality of articles and/or devices wherein each of the articles and/or devices is floating on the surface of the water. The articles, devices, and/or systems may be used for forming oxygen and/or hydrogen gases from water, as described herein.

For embodiments where the article and/or device is to be exposed in water or another liquid, the article and/or device may be formed such that at least some of the core material extends beyond any materials formed on the surface of the core material. This may aid in reducing the distance and/or likelihood that the active components (e.g., anodes, cathodes, etc.) of two different articles and/or devices (e.g., in a system) contact each other. For example, see portion 90 of core material 72 in FIGS. 3E and 3F may act as a bumper.

Those of ordinary skill in the art will be aware of suitable methods for forming the articles and/or devices as described herein. For example, any method which allows for sequential application of the components (e.g., anodes, cathodes, photoactive materials, encapsulant materials, catalytic materials (or precursors) etc.) to a core material may be employed. Non-limiting examples of methods and techniques include etching, lithography, polymerization, deposition (e.g., vapor deposition), etc.

FIG. 4 depicts a non-limiting flow diagram for forming a device (or article) as shown in FIG. 3F. For each of the steps described in this example, the components may be formed using any suitable technique. FIG. 4A shows core material 100, wherein a plurality of anodes 102 are formed on the surface of core material 100. As shown in FIG. 4B, plurality of photoactive material sections 102 may be formed such that at least a portion of one photoactive material section is in contact with each anode. A plurality of cathodes (e.g., 106) may be formed on the core, wherein each cathode is in contact with a single anode, and each cathode is in contact with a photoactive material section (e.g., as shown in FIG. 3C). In FIG. 4D, encapsulant material 108 is applied to the device, wherein the photoactive material section(s) is substantially contained in the encapsulant material. In FIG. 4E, at least one anode is extended (e.g., using material 110, which may be the same or different than material 102) and at least one cathode is extended (e.g., using material 112, which may be the same or different than material 106) beyond encapsulant material 108. FIG. 3F shows an optionally application of anodic catalytic material 114 (or an anodic catalytic material precursor) to extended anode 110. Device 116 is thus formed. FIG. 3G depicts an optionally deployment of a plurality of devices 116 in water, and exposure to electromagnetic radiation 122. The devices shown in FIG. 4G also each comprise stabilizing fin 118 (e.g., as described above). In this figure, the devices were formed to have a select density such that devices float on or near surface 120 of the water.

Those or ordinary skill in the art will be aware of suitable materials to employ as anodes and/or cathodes for use with the articles, devices, systems, and methods as described herein. Generally, the anode(s) and/or cathode(s) comprises a material that is substantially electrically conductive or electrically conductive. The anode(s) and/or cathode(s) may be transparent, semi-transparent, semi-opaque, and/or opaque. In some cases, the anode(s) and/or the cathode(s) are transparent. Non-limiting examples of conductive materials include indium tin oxide (ITO), fluorine tin oxide (FTO), glassy carbon, metals, lithium-containing compounds, metal oxides (e.g., platinum oxide, nickel oxide), graphite, nickel mesh, carbon mesh, and the like. In some cases, the anode(s) and/or cathode(s) may be formed of a metal or metal alloy, for example, comprising copper, silver, platinum, nickel, cadmium, tin, and the like. The anode(s) and/or cathode(s) may also be any other metals and/or non-metals known to those of ordinary skill in the art as conductive (e.g., ceramics). The articles and/or devices of the present invention may be of any size or shape.

The cross-section of the articles and/or devices may be have any arbitrary shape including, but not limited to, circular, square, rectangular, tubular, elliptical, and/or may be a regular or an irregular shape. In some embodiments, for larger articles and/or devices, the articles and/or devices may have an oblong shape. The articles and/or devices may have an average cross-section area of about 10 nm, about 20 nm, about 50 nm, about 100 nm, about 200 nm, about 500 nm, about 1 μm, about 5 μm, about 10 μm, about 50 μm, about 100 μm, about 500 μm, about 1 mm, about 5 mm, about 1 cm, about 2 cm, about 5 cm, about 10 cm, about 50 cm, about 100 cm, or greater. The articles and/or devices may have an average cross-section area of less than about 10 nm, less than about 20 nm, less than about 50 nm, less than about 100 nm, less than about 200 nm, less than about 500 nm, less than about 1 μm, less than about 5 μm, less than about 10 μm, less than about 50 μm, less than about 100 μm, less than about 500 μm, less than about 1 mm, less than about 5 mm, less than about 1 cm, less than about 2 cm, less than about 5 cm, less than about 10 cm, less than about 50 cm, or less than about 100 cm. The articles and/or devices may have an average cross-section area of greater than about 10 nm, greater than about 20 nm, greater than about 50 nm, greater than about 100 nm, greater than about 200 nm, greater than about 500 nm, greater than about 1 μm, greater than about 5 μm, greater than greater than about 10 μm, greater than about 50 μm, greater than about 100 μm, greater than about 500 μm, greater than about 1 mm, greater than about 5 mm, greater than about 1 cm, greater than about 2 cm, greater than about 5 cm, greater than about 10 cm, greater than about 50 cm, or greater than about 100 cm. For elongated articles and/or devices, the aspect ratio of length to width may be about 2:1, or about 5:1, or about 10:1, or about 100:1, or about 500:1, or about 1000:1, or greater.

In some cases, an article and/or device comprises a core material. The core material may be formed as a single section of the article and/or device or alternatively, may comprise a plurality of areas of the article (e.g., as described in FIGS. 2A and 2B) and/or device. In some cases, the core material is substantially the same throughout the article, or alternatively, the core material comprises more than one type of material. Generally, the core is formed of a non-conductive (e.g., insulating) material. Non-limiting examples of non-conductive core materials include, but are not limited to, inorganic substrates (e.g., quartz, glass, etc.) and polymeric materials (e.g., polycarbonate, polystyrene, polypropylene, polyethylene, polymethylmethacrylate, teflon, etc.). In some cases, the core material may comprise a plurality of particles, wherein the anode(s), cathode(s), photoactive material(s), and optionally catalytic material(s) and/or encapsulant material(s) may be formed about the core material. In a specific embodiment, the core material comprises a glass bead and/or a polymeric bead. In some cases, the core material may be transparent or substantially transparent.

In some embodiments, the article and/or devices comprises at least one encapsulant material. Generally, the material is non-conductive. In addition, the encapsulant material may be transparent or substantially transparent. A transparent encapsulant material may allow for the transmission of electromagnetic radiation to reach the photoactive material. The encapsulant material may be the same or different as the material used to form the core. Accordingly, similar non-limiting examples of materials include inorganic substrates and polymeric substrates, as described herein for the core material.

Those of ordinary skill in the art will be aware of suitable photoactive materials for use with the articles, devices, systems, and methods described herein. Generally, the term photoactive material refers to a material that can be used to produce electrical energy from electromagnetic radiation. In some embodiments, the photoactive material is a semiconductor material.

The photoactive material may be selected such that the band gap of the material is between about 1.0 and about 2.0 eV, between about 1.2 and about 1.8 eV, between about 1.4 and about 1.8 eV, between about 1.5 and about 1.7 eV, is about 2.0 eV, or the like. The photoactive material may also have a Fermi level which is compatible with the electrolyte and/or a small work function (e.g., such that electrons may diffuse into the water to attain thermal equilibrium). Non-limiting examples of photoactive materials include TiO₂, WO₃, SrTiO₃, TiO₂—Si, BaTiO₃, LaCrO₃—TiO₂, LaCrO₃—RuO₂, TiO₂—In₂O₃, GaAs, GaP, p-GaAs/n-GaAs/pGa_(0.2)In_(0.48)P, AlGaAs/SiRuO₂, PbO, FeTiO₃, KTaO₃, MnTiO₃, SnO₂, Bi₂O₃, Fe₂O₃ (including hematite), ZnO, CdS, MoS₂, CdTe, CdSe, CdZnTe, ZnTe, HgTe, HgZnTe, HgSe, ZnTe, ZnS, HgCdTe, HgZnSe, etc., or composites thereof. In some cases, the photoactive composition may be doped. For example, TiO₂ may be doped with Y, V, Mo, Cr, Cu, Al, Ta, B, Ru, Mn, Fe, Li, Nb, In, Pb, Ge, C, N, S, etc., and SrTiO₃ may be doped with Zr. The photoactive material may be provided in any suitable morphology or arrangement, for example, including single crystal wafers, coatings (e.g., thin films), etc. Those of ordinary skill in the art will be aware of methods and techniques for preparing a photoactive materials in a chosen form, including, but not limited to, sputtering, sol-gel, and/or anodization.

In some embodiments, a device, article, or system comprising at least one catalytic material. The term “catalytic material” as used herein, means a material that is involved in and increases the rate of a chemical reaction , but is largely unconsumed by the reaction itself, and may participate in multiple chemical transformations. A catalytic material may also be referred to as a catalyst and/or a catalyst composition. A catalytic material is generally not simply a bulk photoactive material. For example, a catalytic material might involve a metal center which undergoes a change from one oxidation state to another during the catalytic process. In another example, the catalytic material might involve metal ionic species which bind to one or more oxygen atoms from water and release the oxygen atoms as dioxygen (i.e., O₂). Thus, catalytic material is given its ordinary meaning in the field in connection with this invention. As will be understood from other descriptions herein, a catalytic material of the invention that may be consumed in slight quantities during some uses and may be, in many embodiments, regenerated to its original chemical state. An anodic catalytic material is a catalytic material associated with an anode, and a cathodic catalytic material is a catalytic material associated with a cathode.

Those of ordinary skill in the art will be aware of suitable catalytic materials to use in connection with the articles, devices, systems and methods of the present invention. In some cases, the cathodic catalytic material catalyzes the formation of hydrogen gas from water and the anodic catalytic material catalyzes the formation of oxygen gas from water. The catalytic material may be formed directly on the article, device, or system, or alternatively, a catalytic material precursor may be formed on the article, device, or system, which may be converted to the catalytic material prior and/or during use of the article, device, or system.

Non-limiting examples of cathodic catalytic materials which may be used for the conversion of water to hydrogen gas include, but are not limited, alloys, metal hydrides, and metals (e.g., platinum).

In some cases, an anodic catalytic material comprises a metal ionic species and an anionic species, according to the methods, guidelines, and parameters described in U.S. Patent Application Publication No. 2010/0101955, filed Jun. 17, 2009, entitled “Catalytic Materials, Electrodes, and Systems for Water Electrolysis and Other Electrochemical Techniques;” U.S. Patent Application Publication No. 2010/0133111, filed Oct. 8, 2009, entitled “Catalytic Materials, Photoanodes, and Photoelectrochemical Cells For Water Electrolysis and Other Electrochemical Techniques;” and U.S. Patent Application Publication No. 2012/0156577, filed Aug. 19, 2011, entitled “Methods for Forming Electrodes for Water Electrolysis and Other Electrochemical Techniques;” each herein incorporated by reference. In some cases, the anodic catalytic material comprises cobalt and/or nickel and anionic species comprising phosphorus and/or boron. In some embodiments, a metal (e.g., cobalt) metal may be formed as an anodic catalytic material precursor on at least one anode, and the anodic catalytic material precursor may be converted to an anodic catalytic material by exposing the device to electromagnetic radiation in the presence of a solution comprising at least on anoinic species (e.g., anionic species comprising phosphorus, anionic species comprising boron, etc.).

In some cases, a catalytic material may associate with another component via formation of a bond, such as an ionic bond, a covalent bond (e.g., carbon-carbon, carbon-oxygen, oxygen-silicon, sulfur-sulfur, phosphorus-nitrogen, carbon-nitrogen, metal-oxygen, or other covalent bonds), a hydrogen bond (e.g., between hydroxyl, amine, carboxyl, thiol, and/or similar functional groups), a dative bond (e.g., complexation or chelation between metal ions and monodentate or multidentate ligands), Van der Waals interactions, and the like. “Association” of a catalytic material with another component would be understood by those of ordinary skill in the art based on this description.

Electromagnetic radiation may be provided by any suitable source. For example, electromagnetic radiation may be provided by sunlight and/or an artificial light source. In an exemplary embodiment, the electromagnetic radiation is provided by sunlight. In some embodiments, light may be provided by sunlight at certain times of operation of a device (e.g., during daytime, on sunny days, etc.) and artificial light may be used at other times of operation of the device (e.g., during nighttime, on cloudy days, etc.). Non-limiting examples of artificial light sources include a lamp (mercury-arc lamp, a xenon-arc lamp, a quartz tungsten filament lamp, etc.), a laser (e.g., argon ion), and/or a solar simulator. The spectra of the artificial light source may be substantially similar or substantially different than the spectra of natural sunlight. The light provided may be infrared (wavelengths between about 1 mm and about 750 nm), visible (wavelengths between about 380 nm and about 750 nm), and/or ultraviolet (wavelengths between about 10 nm and about 380 nm). In some cases, the electromagnetic radiation may be provided at a specific wavelength, or specific ranges of wavelengths, for example, through use of a monochromatic light source or through the use of filters. The power of the electromagnetic radiation may also be varied. For example, the light source provided may have a power of at least about 100 W, at least about 200 W, at least about 300 W, at least about 500 W, at least about 1000 W, or greater.

In some cases, an article, device, system, and/or method as described herein comprises at least one gas collection system. The gas collection system may be used to collect the gas(es) formed by during operation of the article, device, system or method reactions (e.g., oxygen and/or hydrogen formed from the electrolysis of water). In some cases, the gas collection system may be arranged such that each type of gas formed is collected individually. Alternatively, the gas collection system may be arranged such that all types of gases formed are collected by a single gas collection system, and may be later separated.

FIG. 5 depicts a non-limiting of a gas collection system for use with a device or article having an average cross section area of at least about 50 um, or 100 um, or 500 um, or 1 mm, or 5 mm, or 1 cm, or greater. In this example, article or device 120 having first portion 122 in which a first gas (represented by circles 123) is produced and second portion 124 in which a second gas (represented by circles 125) is produced. First portion 122 and second portion 124 are separated by bather 121 which is connected to gas collection container 126. Container 126 has first outlet 130 for collecting gas 123 and second outlet 128 for collecting gas 125. Outlets 128 and 130 may be connected to another system (e.g., wherein the gases such as hydrogen and oxygen gases may be converted back to the original reactant such as water and energy), or may be connected to a gas storage system (e.g., wherein the gases can be stored).

The articles, devices, and systems described herein may be used for a variety of applications relating to photoelectrochemical reactions. In some embodiments, an article, device, and/or system may be used to carry out an photochemical oxidation and/or reduction reaction (e.g., at the surface of water). In some cases, the articles, devices, and/or systems may be used to form hydrogen and/or oxygen gases from water.

In some embodiments, a method of forming oxygen and hydrogen gases from water is provided comprising providing a device, article, or system, comprising at least one anode and at least one cathode and exposing the article, device, or system to electromagnetic radiation thereby forming oxygen gas at the at least one anode and hydrogen gas at the at least one cathode. In some embodiments, the device and/or article comprises first anode and a first cathode, wherein the first cathode is not in physical contact with the first anode; a first photoactive material section, wherein at least a portion of the first photoactive material section is in contact with the first anode and the first cathode; a second anode and a second cathode, wherein the second cathode is not in physical contact with the second anode; and a second photoactive material section, wherein at least a portion of the second photoactive material section is in contact with the second anode and the second cathode, wherein the second anode is in contact with the first cathode and the second cathode is not in contact with the first anode, or alternatively, wherein the second cathode is in contact with the first anode and the second anode is not in contact with the first cathode. In some cases, the article, device, or system does not comprise an external power source.

While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the scope of the present invention.

The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and/or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03. 

1. An article for carrying out an photochemical oxidation and/or reduction reaction at the surface of water, the article comprising: a first anode; a first cathode; and a first photoactive material, wherein at least a portion of the first photoactive material is in electrical communication with the first anode and the first cathode, wherein the article has a density less than or equal to the density of water such that at least a portion of the article, when placed in water, is above the surface of the water.
 2. The article of claim 1, wherein the first cathode is not in physical contact with the first anode.
 3. The article of claim 1, further comprising a core material.
 4. The article of claim 3, wherein the first anode, the first cathode, the first photoactive material, and the core are integrally connected.
 5. The article of claim 1, further comprising: a second anode; a second cathode, wherein the second cathode is not in physical contact with the second anode; and a second photoactive material, wherein at least a portion of the second photoactive material is in contact with the second anode and the second cathode, wherein the second anode is in contact with the first cathode and the second cathode is not in contact with the first anode, or alternatively, wherein the second cathode is in contact with the first anode and the second anode is not in contact with the first cathode.
 6. A device, comprising: a first anode and a first cathode, wherein the first cathode is not in physical contact with the first anode; a first photoactive material section, wherein at least a portion of the first photoactive material section is in contact with the first anode and the first cathode; a second anode and a second cathode, wherein the second cathode is not in physical contact with the second anode; and a second photoactive material section, wherein at least a portion of the second photoactive material section is in contact with the second anode and the second cathode, wherein the second anode is in contact with the first cathode and the second cathode is not in contact with the first anode, or alternatively, wherein the second cathode is in contact with the first anode and the second anode is not in contact with the first cathode.
 7. A method of forming oxygen and hydrogen gases from water, comprising: providing a device, comprising: a first anode and a first cathode, wherein the first cathode is not in physical contact with the first anode; a first photoactive material section, wherein at least a portion of the first photoactive material section is in contact with the first anode and the first cathode; a second anode and a second cathode, wherein the second cathode is not in physical contact with the second anode; and a second photoactive material section, wherein at least a portion of the second photoactive material section is in contact with the second anode and the second cathode, wherein the second anode is in contact with the first cathode and the second cathode is not in contact with the first anode, or alternatively, wherein the second cathode is in contact with the first anode and the second anode is not in contact with the first cathode, and wherein the device does not comprise an external power source; and exposing the device to electromagnetic radiation thereby forming oxygen gas at the at least one anode and hydrogen gas at the at least one cathode.
 8. The article of claim 1, wherein the first anode is associated with an anodic catalytic material.
 9. The article of claim 1, wherein the second cathode is associated with a cathodic catalytic material.
 10. The article of claim 1, further comprising at least one stabilizing fin.
 11. (canceled)
 12. (canceled)
 13. The article of claim 1, wherein at least a portion of the article is encapsulated with an encapsulant material.
 14. (canceled)
 15. (canceled)
 16. The article of claim 5, further comprising: a third anode; a third cathode, wherein the third cathode is not in physical contact with the third anode; and a third photoactive material section, wherein at least a portion of the third photoactive material section is in contact with the third anode and the third cathode, wherein the third cathode is in contact with the second cathode and the third cathode is not in contact with the first anode or the second anode, or alternatively, wherein the third cathode is in contact with the second anode and the third anode is not in contact with the first cathode or the second cathode.
 17. (canceled)
 18. The article of claim 1, wherein the first anode is in direct electrical communication with the first photoactive material and/or the first cathode is in direct electrical communication with the first photoactive material.
 19. The article or a method of claim 1, wherein the first anode is in indirect electrical communication with the first photoactive material and/or the first cathode is in indirect electrical communication with the first photoactive material.
 20. The article of claim 5, wherein the second anode is in direct electrical communication with the second photoactive material and/or the second cathode is in direct electrical communication with the second photoactive material.
 21. The article of claim 5, wherein the second anode is in indirect electrical communication with the second photoactive material and/or the second cathode is in indirect electrical communication with the second photoactive material.
 22. The article of claim 5, wherein at least one anode is capable of carrying out an oxidation reaction and/or at least one cathode is capable of carrying out a reduction reaction.
 23. The article of claim 1, wherein the article has an average cross section area of at least about 10 nm, about 20 nm, about 50 nm, about 100 nm, about 200 nm, about 500 nm, about 1 μm, about 5 μm, about 10 μm, about 50 μm, about 100 μm, about 500 μm, about 1 mm, about 5 mm, about 1 cm, about 2 cm, about 5 cm, about 10 cm, about 50 cm, or about 100 cm.
 24. (canceled)
 25. (canceled)
 26. The device of claim 6, wherein the device has a density less than or equal to the density of water such that at least a portion of the device, when placed in water, is above the surface of the water.
 27. (canceled)
 28. A system comprising a plurality of articles as in claim
 1. 29. (canceled) 